Physical-layer Network Coding (PNC)

Physical-layer Network Coding (PNC) was invented by Co-I Prof. Soung Chang Liew and his students in 2006. It is about applying the principle of NC by allowing EM waves to add up physically in a wireless broadcast situation. PNC has become an important subfield of NC. It is catching much attention in the research community, and there have been a few special issues on PNC organized by various academic journals.

In March 2011, our team successfully built a software radio prototype that demonstrates for the first time the principle of PNC. This prototype implements PNC in the frequency domain using the OFDM technology. As a result of this first investigation, a number of technical issues unique to PNC were uncovered and this added much energy to the ongoing theoretical research in the team.

In the second half of 2012, the team completed the first real-time prototype that allows file exchange between two nodes via a PNC relay in real-time ( A MAC protocol has been implemented to coordinate the simultaneous transmissions of the two nodes. Ongoing efforts focus on improving the efficiency, throughput, and reliability of the real-time system. Our demo video can be found in ( and (

In the first quarter of 2013, the team successfully demonstrated a first wireless local area network (WLAN) system that jointly exploits physical-layer network coding (PNC) and multiuser decoding (MUD), called network-coded multiple access (NCMA), to boost system throughput. Prior studies on PNC mostly focused on relay networks – generally network coding could play a major role only in relay networks (wired or wireless) in which network coding is performed by the relays. This is the first realized multiple access scheme that establishes the usefulness of PNC in a non-relay setting. In the last quarter of 2014, a real-time NCMA system that can outperform conventional WLAN by 100% in terms of throughput was built.

Building on our success in establishing the soft radio expertise, we organized several software radio implementation workshops: SRIF 2012 held at CUHK on Jan 12-13, 2012 (; SRIF 2013 as an ACM SIGCOMM Workshop in Aug 2013 (; and SRIF 2014 ( held in conjunction with ACM SIGCOMM again in Chicago.

We are collaborating with DLR (German Aerospace Center) to explore the applications of PNC and NCMA in satellite networks. This is a long-term initiative that will straddle across a number of years. To kick-start the collaboration, in March 2014, we co-hosted a workshop ( in Shenzhen, sponsored by the Sino-German Research Grant.